REPAIRING ECOSYSTEMS—HABITAT COMPONENTS AND ANIMAL BEHAVIOR

The arrangement of habitat components across a landscape is vastly different for animals in a prairie, forest (or anywhere else, for that matter) than for people in a city because we, the people, rearrange land on which we build our own shelters, to which we bring food and water from afar. Moreover, many people throughout the world can routinely store excess food for long periods in freezers, regardless of weather or climatic conditions. In contrast, nature creates habitable areas within a landscape (a snag of the right size, a fallen tree under which to dig, a cliff that ameliorates the ambient temperature, and so on), not the animals that need them. Animals must find their required ration of food and water on a daily basis, and many must locate existing or potential shelter as well. Another circumstance—the connectivity of habitat components in and across the landscape—is equal in importance.

Proximity to food, water, and shelter is critically important for the most sedentary and highly adapted species (such as salamanders). Proximity to food, water, and shelter is progressively less important for the most wide-ranging and adaptable species (such as coyotes, mountain lions, and elk), which can travel great distances in short periods of time. However, wide-ranging species that live in ever-more fragmented habitats require safe corridors for travel through hostile terrain from one habitat component to another. Let’s take a quick look at a few of the possibilities.

WATER

A salamander or a frog cannot travel a mile to get a drink of water, but an elk, a bear, or a mountain lion can. By the same token, an eagle can fly a great distance to water, but most bats require drinking water within roughly a 1/4 mile of their daytime roosts or nursery colonies.

As an aside, an adaptation to the problem of getting water is that of the sandgrouse (a bird the size of a small chicken), which I saw in the Egyptian and Nubian deserts. Sandgrouse nest well away from water, which minimizes the potential predation on their young, but their offspring require water nonetheless. Sandgrouse therefore fly great distances to water, soak their breast feathers in the precious liquid, and fly back to their nests to give their offspring a drink of the water stored in their feathers. On the other hand, food is not such a problem because it is more widely distributed than water throughout the sandgrouse’s desert habitat.

FOOD

Grazers, such as deer, require food and cover in close proximity because they are vulnerable to mountain lions and other predators while feeding. Thus, they venture from cover, eat rapidly, and return to cover, where, in relative safety, they chew their cud (regurgitated food), which corresponds to eating their food a second time. Deer also migrate from a summer range to a winter range and back again, meaning they need a good-quality corridor within which to travel.

Small forest animals, such as amphibians, shrews, and mice, use the open, downhill side of logs as a protective cover while navigating the surface of the forest floor in search of food—an idea emulated by the concrete tunnels open on the downhill side that protect traffic from snowdrifts and avalanches in the Austrian Alps and the higher elevations of Japan. Ants, however, create open highways in areas of dense, herbaceous vegetation, which forms the first stage of forest development; these highways are often crowded with hundreds of individuals going far afield from their colony in search of food. In addition, some rodents make aboveground runways from one fallen tree to another through the herbaceous ground cover, but they construct belowground burrows at other times in order to connect one place with another. Belowground burrow systems are also the preferred mode of travel for pocket gophers as they forage, although they construct aboveground burrow systems through the snow in winter.

Other animals, like river otters, seem to have a wanderlust and travel great distances to fulfill their requirements, which include a prodigious amount of playtime. The marten, a cousin of the otter, is also a traveler, but stays within forested areas, where its prey base is located; the marten is thus constrained in its movements by such habitat alterations as clear-cut logging because it will not readily venture into such open areas. Bobcats, which are stalkers, require sufficient cover in order to ambush their prey, but coyotes, which are chasers, require open areas in order to run their prey to ground.

SHELTER

Some small mammals have everything neatly packaged. Water voles live along streams in the higher elevations of western North America, where they use both the waterways and runways through herbaceous vegetation on the streams’ banks to move about and obtain their vegetarian food. In addition, they burrow into the stream banks, where they build snug nests and have all their life’s necessities in immediate proximity.

Birds and bats, however, spend time away from their living quarters (cavities in snags, nests in shrubs and trees, caves, and so on) while they forage and quench their thirst. Being aerially mobile, they are relatively free to move about and stitch their habitat requirements together with greater facility than some of their earth-bound kin.

Still others, such as male mountain lions and elk, traverse great distances in search of food, water, and shelter. To them, “home is where their rump rests” on any given day.

SPACE

Not only is the arrangement of habitat components important to animals but so too is the habitat’s extent. To illustrate, the water vole requires but a small area along a mountain stream in order to have a viable lifestyle. Compared with water voles, coyotes are exceedingly adaptable, relatively wide-ranging, independent animals that can seemingly survive anywhere, including in the suburbs of Los Angeles, California, where they help themselves to garden produce, scraps of human food, and food left out for pets. In addition, they are quite willing to eat neighborhood cats, chickens, ducks, and any other handy foods.

Roaming the country singly, in pairs, or as family groups, coyotes prey on a wide array of animals, beginning (as pups) with grasshoppers and graduating (as adults) to prey as large as adult mule deer and yearling domestic cattle or any other seasonal morsel they deem tasty. Coyotes are also adept at dining on fruits, a habit that has earned them the nickname melon wolves in some parts of their geographical distribution because they steal from farmers’ fields.

As a generalist, the coyote can survive under a wide range of environmental conditions, from Texas to Alaska and from the Pacific Northwest to the Eastern Seaboard. Their arrival in Alaska and on the Eastern Seaboard is relatively recent and is due primarily to the clear-cutting of vast areas of dense forest. Our social activities have opened thousands of square miles for the coyote to inhabit because of its extraordinary adaptability. And because of its wide array of possible food items, the coyote can make use of a broad variety of energy sources.

Unlike coyotes, wolves are social animals that live in packs. Their group life places limits on their ability to use habitats. For example, a far greater number of coyotes than wolves can live in Yellowstone National Park in Wyoming because a pack of wolves acts as a single, large organism and therefore requires a much vaster area in which to hunt. A pair of coyotes can live on rabbits and fruits in season, but a pack of five to seven wolves, each of which is much larger than even a big coyote, acts collectively as a single, large animal that must continually secure prey the size of deer, elk, and North American moose in order to survive.

A pack of wolves has a much harder time staying fed than does a pair of coyotes. It takes far more time, energy, and trials for a pack of wolves to select, chase, and bring down large prey at any time of the year than it does for a coyote, which at certain times of the year can make do quite nicely on a diet of grasshoppers, meadow mice, and ripe berries.

As a specialist, the wolf is fitted to a narrow set of environmental circumstances and can survive only it if finds sufficient prey large enough to feed the pack as a whole. The wolf, therefore, has a limited range of prey items to which it is effectively adapted as sources of energy, and it can neither fit itself to a wide variety of conditions nor fit a wide variety of conditions to itself.

These requirements make the wolf, as a highly adapted social specialist, vulnerable to extinction because of humanity’s continual encroachment on and fragmentation of its habitat, while the coyote, as a supremely adaptable, individualistic generalist, is likely to out-survive humanity itself. This outcome is particularly evident as the wolf’s geographical range shrinks in the face of societal pressures on the landscape, while the coyote’s geographical range increases in concert with those same pressures.

PRIVACY

With respect to privacy, the little water vole can probably satisfy this requirement privacy most easily because privacy is only a burrow away. But the medium-sized coyote is so adaptable and individualistic that it can find privacy almost anywhere. For a large pack of wolves in a progressively fragmented habitat, privacy is becoming increasingly rare, and this lack of privacy is part of the reason so much of their former geographical range is no longer suited for them to inhabit.1 Beyond understanding the components of habitat, we need to know how they are configured into landscape patterns so we can emulate them in order to repair an ecosystem, such as a prairie.